1. Field of the Invention
The present invention relates to a liquid discharge head and a manufacturing method of a liquid discharge head.
2. Description of the Related Art
A liquid discharge apparatus represented by an ink jet recording apparatus induces film boiling of ink using thermal energy generated by an energy generating element formed on a liquid discharge head. Then, the liquid discharge apparatus discharges ink to a recording medium using bubble pressure produced by the film boiling of ink to perform recording operation. The liquid discharge head includes a liquid discharge head substrate containing the energy generating elements arranged in row on the surface thereof, and a discharge port member containing a discharge port, joined with the liquid discharge head substrate. The liquid discharge head needs to have heat storage performance to transfer heat generated by the energy generating elements to ink effectively. Japanese Patent Application Laid-Open No. 2005-280179 discusses a liquid discharge head in which a heat storage layer composed of silicon oxide is provided between an energy generating element on the liquid discharge head substrate and a board composed of silicon to secure the heat storage performance.
On the other hand, to avoid an excessive rise of the temperature of the liquid discharge head, excessive heat excluding a heat necessary for the above-described heat storage operation must be released out of the liquid discharge head appropriately. Japanese Patent Application Laid-Open No. 2002-11882 discusses a liquid discharge head capable of releasing such excessive heat by extending a cavitation-resistant metal layer provided on the energy generating element to transfer part of the heat generated by the energy generating element. As described above, the liquid discharge head is provided to release the excessive heat while maintaining the heat storage performance to achieve an effective recording operation.
When the recording operation is executed continuously using the liquid discharge head substrate containing an energy generating element row (hereinafter element row), the temperature of the substrate rises due to a heat generated by the energy generating elements. In this case, heat can be released more easily to a non-heat generation region outside of the element row at nearer an end portion of the element row than at the central portion thereof. Accordingly, a difference in temperature occurs between near the end portion and the central portion of the element row in the liquid discharge head substrate. According to the method discussed in Japanese Patent Application Laid-Open No. 2002-11882, the heat dissipation metal layer is formed to meet each of the energy generating elements equally, so that the difference in temperature cannot be eliminated.
With the difference in temperature generated in the head substrate, a difference occurs also in viscosity of the liquid to be discharged, between at the central portion and the end portion of the element row. As a result, dispersion occurs in the amount of liquid droplet ejected from discharge ports, and therefore, there exists a fear that the quality of recorded images may be deteriorated.